The present invention relates to panels and a method of making such panels as well as to reinforcing structures and a method of making such structures and in particular to aircraft panels.
FIG. 1 is a cross-sectional view through a part of a known racelle structure.
The section shows a honeycomb structure 11 on an outer skin 13 and a honeycomb structure 15 on an inner skin 10. The section is built up in a series of manufacturing step comprising:
laying the skin 10 onto a former and curing that skin,
laying the honeycomb structure 15 onto the skin,
laying peripheral skins 17 around the periphery of the structures 15 to hold the structures 15 in place.
The inner skin 10 is then perforated by drilling to allow the acoustic honeycomb panels to reduce the sound emitted from the thrust reverser.
The outer skin is then formed in a similar manner and connected to the inner skin by riveting end sections 19 and 21 to both sections and riveting an intermediate connection member 23 to both sections.
The inner and outer skins thus form a structural one piece unit having considerable strength and rigidity. There are, though, disadvantages with such an aircraft panel.
One disadvantage are the many manufacturing steps required to make the panel. The outer skin is first formed in its various stages, then the honeycomb structures are attached, then the inner skin with its many manufacturing stages is attached. This is time consuming. Furthermore, it is time consuming to attach all of the rivets. A further disadvantage in the manufacturing procedure is that the inner skin is formed in a series of steps, before being rivetted to the outer skin.
The honeycomb provides noise attenuation and strength. However, the skin 10 has to be drilled in order for the honeycomb action to act as a noise attenuator thereby significantly reducing the strength of the panel.
Apart from the manufacturing problems there are also significant operational problems. Should the outer surface of the outer skin be subject to an impact from a dropped tool or be struck by a truck, for instance, the necessary rigidity of the one piece structural panel acts against the panel being able to resist impact damage. Such a panel would suffer damage necessitating repair prior to flying again under an impact of as little as 5 Joules. Repair of the honeycomb is extremely expensive.
Furthermore, if the panel is damaged, the complete door will require replacement as the inner and outer skins act together to provide the reinforced structure. Thus, a damaged outer skin cannot be patched up and it is necessary to ground the aircraft until a new panel can be fitted. Furthermore, to repair the panel or to inspect the internal parts of the panel just in case they have been damaged by an impact it is necessary to dismantle the panel by removing the numerous connecting riverts. This is not a facility available at most airports. Consequently a new panel has to be flown in and the old panel taken elsewhere for disassembly, repair and reconstrunction.
It is an object of the present invention to attempt to overcome at least some of the above described disadvantages.
According to one aspect of the present invention a panel comprises a first skin structure incorporating a first skin and a second skin structure incorporating a second skin, part of the second skin being movable towards the first skin.
The first skin structure may be relatively rigid compared to the second skin structure. The second skin structure may be flexible relative to the first skin structure.
The second skin structure may be more flexible than the first skin structure.
The first and second skin structures may be connected together and may be detachably connected together, for instance by releasable fasteners.
The first and second skin structures may be connected together at a peripheral region.
The first and second skin structures may be separate from each other at locations in from the peripheral region of those structures. The first and second skin structures may be spaced from each other at all locations in from the peripheral regions of those structures.
The first and second skins may define a cavity between them. The first skin structure may include a noise abatement portion and the noise abatement portion may extend inwardly of the external surface of the first skin. The first skin may be perforated in the region of the noise abatement portion.
The noise abatement portion itself may comprise an antennae or an electronics device.
The part of the second skin that is movable towards the first skin may be arranged to flex towards the first skin when subject to an impact. The part of the second skin that has flexed towards the first skin may be arranged to flex back to its previous configuration after the impact.
The first, skin structure or, alternatively or additionally, the second skin structure may include flanged strengthening portions connected to the skins extending inwardly of the cavity. When both the first and second skin structures include flanged strengthening portions the second skin strengthening portion may be arranged to move between flanged strengthening portions of the first skin when the second skin moves towards the first skin.
When the first skin structure includes at least one strengthening portion, the second skin, when flexed towards the first skin, may be arranged to abut the strengthening portion on the first skin. When the second skin structure also includes at least one strengthening portion, flexure of the second skin structure towards the first skin structure may be arranged to cause the second skin to abut with the strengthening portion of the first skin structure rather than the strengthening portion of the second skin structure contacting the first skin.
The first skin structure may include at least one flanged strengthening portion facing the second skin and extending over the noise abatement portion and possibly to at least one side or both sides of the noise abatement portion. When the flanged strengthening portion extends to one or both sides of the noise abatement portion the extent of the flanged strengthening portion into the cavity from the first skin or the extent towards the second skin may be substantially constant along the length of the strengthening portion.
The first skin structure may comprise an inner skin structure and the second skin structure may comprise an outer skin structure.
The panel may be an aircraft panel.
The aircraft panel may comprise part of a thrust reverser or may comprise a fan duct structure.
According to another aspect of the present invention a method of making a skin structure of an aircraft panel comprises laying at least one flexible filamentary layer onto a support shaped so as to locate a noise abatement portion before causing the or each flexible filamentary layer to harden.
The noise abatement portions may comprise an antennae or an electronic device.
Subsequently, the noise abatement portion may be located onto the filamentary layer and subsequently at least one further flexible filamentary layer may be located over the noise abatement structure before causing the flexible filamentary layers to harden.
The method may comprise locating at least one flanged flexible filamentary portion on to a flexible filamentary layer before causing the filamentary layers and filamentary portion to harden. The method may comprise locating the flanged flexible portion over the filamentary layer that extends over the noise abatement portion and possibly beyond the noise abatement structure to at least one side before causing the filamentary layers and the flexbile portion to harden. The method may comprise making the uppermost extent of the flanged flexible portion a substantially constant distance from the downwardly facing surface of the lowermost filamentary layers.
The present invention also includes a skin structure when made according to the aforementioned method.
According to a further aspect of the present invention an aircraft panel comprises at least one skin extending over substantially the complete extent of the panel, the panel including a noise abatement structure attached to the skin, the noise abatement structure being covered with a sheet, the sheet having perforations therethrough.
With such a panel, the panel has strength in the continuous skin without the skin being perforated and yet the skin still has the noise abatement advantages.
The noise abatement structure may comprise an antennae or an electronic device.
The sheet may be arranged to be on the outside of the panel.
The skin may include at least one stiffener on the opposite side of the skin to the noise abatement structure.
According to a further aspect of the present invention a reinforced structure comprises a plurality of arms extending from different directions towards a common junction, each arm including at least one layer of fibrous material extending both in a first direction and in a second direction transverse to the first direction, at least one of those layers of two adjacent arms being common to those arms.
The noise abatement structure may be located in a recess of the skin. The sheet and the skin may form a substantially continuous surface.
The layer that is common between adjacent arms may have a generally U-shaped cross-section along each arm.
The structure may have a plurality of layers that are in common with adjacent arms.
The present invention also includes a method of making a reinforced structure comprising a plurality of arms extending from different directions towards a common junction, the method comprising laying at least one fibrous layer to extend along one arm in a first direction and a second direction transverse thereto with the layer also being laid along an adjacent arm to also extend in a first direction and a second direction transverse thereto.
According to another aspect of the present invention a reinforced structure comprising a plurality of arms extending from different directions towards a common junction comprises each arm including a plurality of parallel fibrous layers extending towards the common junction with a first layer of one arm being common with a layer of an adjacent arm on one side of that arm and a second layer of that arm being in common with the layer of an adjacent arm on the other side of that arm, the first and second layers contacting each other at their co-extent on each arm.
The present invention also includes a method of making a reinforced structure comprises a plurality of arms extending from different directions towards a common junction, the method comprising laying two parallel layers in contact with each other along one arm with those layers extending towards the junction and then away from the junction along different arms on either side of the arm that they are in contact with each other along.
According to another aspect of the present invention a method of making a reinforced structure comprising a plurality of arms extending from different directions towards a common junction comprises placing a layer of fibrous material around a central region of the junction and laying fibrous layers from each arm to extend towards the junction from one arm and subsequently away from the junction along an adjacent arm with the laid fibrous layers subsequently being caused to harden substantially simultaneously.
The present invention also includes a method of making such a reinforced structure comprising laying the layer that extends along one arm towards the junction and then away from the junction along a different arm in contact with the layer that extends around the central region of the junction.
The present invention also includes a reinforced structure made by such a method.
A reinforced structure as herein described may comprise the depth of an arm or flange on one side of the junction increasing or decreasing in the direction towards the junction. The depth of an arm or flange on the other side of the junction may decrease or increase in a direction away from the junction.
The depth of arms or flanges extending transverse to the arm on one side and the arm on the other side of the junction may be substantially constant.
The reinforced structure may include two junctions that one arm or flange extends between.
The present invention includes any combination of the herein referred to features or limitations and includes a method of making a reinforced structure as herein referred to and a reinforced structure made by such a method.